View source for Failure Analysis – Basics

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<span style="font-size:1.2em;font-weight:bold;">Failure analysis – Basics</span>
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==Failure analysis, evaluation of damage cases==

Damage analyses serve to determine the causes of [[Plastic Component|component]] failure and to draw conclusions from this in order to initiate targeted measures for damage repair and prevention.

A wide range of analytical methods, [[Polymer Testing|polymer testing]] and [[Polymer Diagnostic|polymer diagnostics]] are available for damage analysis on [[Plastics|plastics]].

Compared to metallic [[Material & Werkstoff|materials]], the properties of [[Plastic Component|plastic components]] are much more strongly influenced by design, material selection and processing and machining conditions. These influencing factors must therefore be given special consideration when performing damage analyses on plastics.

The wide range of possible polymer modifications and the use of [[Particle-filled Thermoplastics|fillers]] and reinforcing materials (see: [[Fibre-reinforced Plastics|fibre-reinforced plastics]]), additives and stabilisers result in a wide variety of failure and damage mechanisms in practical use, which can significantly affect the functional integrity of the component.

Plastic components are often subjected to very complex mechanical, thermal, media and climatic [[Stress|stresses]] during use, which, in conjunction with [[Ageing|ageing]] and degradation effects, can lead to [[Component Failure|component failure]] due to [[Fracture|fracture]].

As a result of the inherent [[Creep Plastics|creep tendency of plastics]] and the [[Relaxation Plastics|relaxation conditions]] that occur, either plastic instability with impermissibly large [[Deformation|deformations]] or unstable [[Crack Propagation|crack propagation]] can occur in conjunction with the [[Tensile Test Residual Stresses Orientations|residual stress and orientation state]] as well as the [[Viscoelastic Material Behaviour|viscoelastic deformation behaviour]].

==Failure analysis, fracture surface analysis==

Fracture surface analysis allows initial conclusions to be drawn about the [[Fracture Types|type of failure]] and the conditions under which it occurred. Even with the naked eye or with the aid of a microscope, it is possible to distinguish between a brittle fracture and a [[Ductility Plastics|ductile]] [[Fracture Types|fracture]]. It is also possible to determine whether the damaged component was subjected to [[Quasi-static Test Methods|static]], [[Impact Loading Plastics|impact]] or cyclic (e.g. oscillating) stress prior to the [[Fracture|fracture]] (see also: [[Fatigue|fatigue]]).

[[File:Pendel_Bild.jpg]]
{| 
|- valign="top"
|width="50px"|'''Figure''': 
|width="600px" |[[Fracture Surface|Fracture surface]] of a component made of high-density polyethylene ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PE-HD) after cyclic stress
|}

==Failure analysis, complexity==

Damage is defined as changes to a [[Component Testing|component]] that significantly impair or prevent its intended function, whereby the cause of damage is the sum of the factors that caused the damage.

In [[Failure Analysis Plastics Products, VDI Guideline 3822|damage analysis]], the type and cause of damage are determined from the damage pattern – the apparent damage phenomena.

The following damage phenomena occur most frequently in [[Plastic Component|plastic components]]:

* [[Deformation#Plastic deformation|Plastic deformation]], deforming
* [[Crack Formation|Crack formation]]
* [[Fracture]]
* [[Surface Testing Technology|Surface damage]]
* Discolouration

One of the most common causes of catastrophic failure is the brittle fracture of components or component parts (see: [[Fracture Types|types of fracture]]). Brittle fracture is promoted by various influencing factors, which can occur either individually or in combination (see: [[Brittle Fracture Promoting Factors|brittle fracture promoting factors]]).

[[File:Scheme - Brittle Fracture.jpg|600px]]
{| 
|- valign="top"
|width="50px"|'''Figure''': 
|width="600px" |Factors promoting brittle fracture in plastic components
|}

Component damage occurs when the [[Material & Werkstoff|material's]] property profile (physical, mechanical, thermal and chemical properties) does not match the component's requirement profile.

==Failure analysis, mechanical stress==

If a component fails during use as a result of mechanical [[Stress|stress]] alone, it can be assumed that this component was subjected to stress exceeding the permissible load limit specified in the component design or that it was not used for its intended purpose, i.e. that it was overloaded (see: [[Plastic Component|plastic component]], dimensioning).

[[File:RTEmagicC_mindmap_neu(engl.).jpg|600px]]
{| 
|- valign="top"
|width="50px"|'''Figure''': 
|width="600px" |Damage caused by mechanical stress – damage phenomena, causes of damage and evidence of damage
|}

[[Component Failure|Component failure]] due to mechanical [[Stress|stress]] in the subcritical range, on the other hand, is an indication that the actual cause of damage is not to be found in the mechanical stress itself, but rather in the component design, the choice of materials, the quality of manufacturing or the effects of external influences (temperature, media, radiation, etc.). The mechanical [[Stress|stress]] on already damaged components is then ultimately the load that leads to the final component failure. If, for example, media stress causes embrittlement of the [[Material & Werkstoff|material]] and associated crack formation (see: [[Crack Formation|crack formation]]), additional mechanical stress leads to the [[Crack Opening|opening of the crack]] flanks, associated [[Crack Propagation|crack propagation]] and ultimately to [[Fracture|fracture]], the final failure of the component, which is associated with material separation leading to a loss of load-bearing capacity.

==See also==

* [[Fibre-reinforced Plastics|Fibre-reinforced plastics]]
* [[Fracture]]
* [[Fracture Types|Fracture types]]
* [[Fracture Formation|Fracture formation]]
* [[Fatigue]]
* [[Brittle Fracture Promoting Factors|Brittle fracture promoting factors]]
* [[Failure Analysis Plastics Products, VDI Guideline 3822|Failure analysis of plastic products, VDI Guideline 3822]]
* [[Deformation Mechanisms|Deformation mechanisms]]
* [[Plastic Component|Plastic component]]

==References==

* Kotter, I., [[Grellmann,_Wolfgang|Grellmann, W.]]: Schadensanalyse an Kunststoffprodukten – Die VDI-Richtlinie 3822 in der praktischen Anwendung. 23. Fachtagung über Verarbeitung und Anwendung von Polymeren "Technomer 2013", Chemnitz, November 14–15, 2013, Proceedings (CD-ROM), KP v 8.6 pp. 1–6
* Zankel, A., Chernev, B., Brandl, C., Poelt, P., Wilhelm, P., Nase, M., Langer, B., [https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.], Baumann, H.-J.: Estimation of beam damage of polymers caused by In-situ investigations in the ESEM using IR-spectroscopy. Macromolecular Symposia 265 (2008) 156–165 DOI: https://doi.org/10.1002/MASY.200850517
* Langer, B., [https://researchgate.net/profile/Ralf-Lach Lach, R.], [https://de.wikipedia.org/wiki/Wolfgang_Grellmann Grellmann, W.]: Bruchmechanische Kennwertermittlung für Kunststoffe – Beispiele aus der Diagnostik und Schadensfallanalyse. In: Frenz, H., Grellmann, W. (Eds.): Herausforderung neuer Werkstoffe an die Forschung und Werkstoffprüfung, 26. Vortrags- und Diskussionstagung Werkstoffprüfung 2008, December 4 – 5, 2008, Berlin, (ISBN 978-3-00-026399-6), Proceedings pp. 289–294
* Kotter, I., Grellmann, W.: Schadensanalyse an Kunststoffen – Mechanische Beanspruchung als Indikator. Proceedings Technomer 2009 (CD-ROM), November 12–14, 2009, Chemnitz, Themenkomplex Prüftechnik und Qualitätssicherung, PQV 8, pp. 1–6
* Kotter, I., Grellmann, W.: Schäden infolge mechanischer Beanspruchung – Indikator oder Überlastung? VDI-Seminar 350602 "Fehler- und Schadensanalyse an Kunststoffprodukten", Aachen, December 4 – 5, 2008, Proceedings pp. 5.1–5.24
* Kotter, I., Grellmann, W.: Kunststoffdiagnostik und Schadensanalyse – Charakteristische Beispiele. In: Borsutzki, M., Geisler, S.: Fortschritte der Kennwertermittlung für Forschung und Praxis (Proceedings Werkstoffprüfung 2009, December 3 – 4, 2009, Bad Neuenahr), Publishing House Stahleisen, Düsseldorf 2009, pp. 377–382, (ISBN 978-3-514-00769-7)
* Vesely, P., Kotter, I., Lach, R., Nezbedova, E., Knesl, Z., Hutar, P., Grellmann, W.: Prüfmethoden zur Analyse des lokalen mechanischen Verhaltens von Schweißnähten in Polyethylen-Kunststoffrohren. In: Borsutzki, M., Geisler, S. (Eds.): Fortschritte der Kennwertermittlung für Forschung und Praxis (Proceedings Werkstoffprüfung 2009, December 3 – 4, 2009, Bad Neuenahr), Publishing House Stahleisen, Düsseldorf 2009, pp. 371–376, (ISBN 978-3-514-00769-7)
* Kotter, I., Grellmann, W.: Schäden als Folge mechanischer Beanspruchung – Indikator oder Überlastung? 12. Tagung "Problemseminar Deformation und Bruchverhalten von Kunststoffen", June 24 – 26, 2009, Merseburg, Proceedings CD-ROM (ISBN 978-3-86829-170-4), pp. 19–23
* Kotter, I., Dahlmann, R., Grellmann, W.: Schadensanalyse an Kunststoffprodukten. 12. Tagung "Problemseminar Deformation und Bruchverhalten von Kunststoffen", June 24 – 26, 2009, Merseburg, Proceedings CD-ROM (ISBN 978-3-86829-170-4), pp. 350–352
* Vesely, P., Kotter, I., Lach, R., Nezbedova, E., Hutar, P., Grellmann, W.: Mechanical and Fracture Behaviour of Plastic Pipes with and without Butt-Welded Joints. 12. Tagung "Problemseminar Deformation und Bruchverhalten von Kunststoffen", June 24 – 26, 2009, Merseburg, Proceedings CD-ROM (ISBN 978-3-86829-170-4), pp. 395–400
* [[Bierögel, Christian|Bierögel, C.]], Grellmann, W., Fahnert, T., Lach, R.: Laserextensometrie – Charakterisierung von Schweiß- und Bindenähten an Kunststoffen. In: Borsutzki, M., Geisler, S.: Fortschritte der Kennwertermittlung für Forschung und Praxis, Tagung Werkstoffprüfung, December 7 – 8, 2006, Bad Neuenahr, Proceedings, (ISBN 978-3-514-00734-5) pp. 433–438
* Kotter, I., Langer, B., Bierögel, C., Grellmann, W.: Technische Kunststoffdiagnostik – Schadensanalyse an Kunststoffbauteilen. In: [https://de.wikipedia.org/wiki/Michael_Pohl_(Metallurg) Pohl, M.]: Konstruktion, Qualitätssicherung und Schadensanalyse, Tagung Werkstoffprüfung 2007, November 29 – 30, 2007, Neu-Ulm, Tagungsband No. 298, pp. 273–278
* Kotter, I., Langer, B., Bierögel, C., Grellmann, W.: Technische Polymerdiagnostik – Beispiele zur Schadensanalyse an Kunststoffbauteilen. 11. Tagung Problemseminar: Deformation und Bruchverhalten von Kunststoffen, June 20–22, 2007, Merseburg, Proceedings (CD-ROM), pp. 47–53
* Kotter, I., Grellmann, W.: Schadensanalyse an Kunststoffprodukten – Beispiele aus der Praxis. In: Borsutzki, M. und Moginger, G. (Eds.): Fortschritte in der Werkstoffprüfung für Forschung und Praxis. Tagung Werkstoffprüfung 2012, December 6 – 7, 2012, Bad Neuenahr, Proceedings pp. 317–322, (ISBN 978-3-514-00794-9)
* Kotter, I., Grellmann, W.: Failure Analysis of Thermoplastics Products – Practical Examples. 15th International Conference "Polymeric Materials", Halle/Saale, September 12–14, 2012 proceedings (CD-ROM), P 37, pp. 1–10
* Kotter, I., Grellmann, W.: Failure Analysis of Thermoplastics Products – Practical Examples. 14. Problemseminar "Deformation und Bruchverhalten von Kunststoffen" June 25 – 27, 2014, Merseburg, Proceedings pp. 545–555 (ISBN 978-3-942703-30-7)
* Kotter, I., Grellmann, W.: Die Fraktographie als Hilfsmittel in der Schadensanalyse – Möglichkeiten und Grenzen. 14. Problemseminar "Deformation und Bruchverhalten von Kunststoffen", Merseburg, June 25–27, 2014, Merseburg, Proceedings pp. 18–26 (ISBN 978-3-942703-30-7)
* [[Reincke,_Katrin|Reincke, K.]]: Schadensanalyse an Elastomerbauteilen. In: Frenz, H., Langer, J. B. (Eds.): Fortschritte in der Werkstoffprüfung für Forschung und Praxis. Prüftechnik – Kennwertermittlung – Schadensvermeidung, (ISBN 978-3-9814516-7-2; see [[AMK-Library]] under A 20), Tagungsband "Werkstoffprüfung 2017", November 30 – December 1, 2017 Berlin, pp. 17–22

[[Category:Damage Analysis_Component Failure]]
[[Category: Ageing]]